Motor vehicles use various mechanisms to facilitate braking. Well known among these braking mechanisms is a combination of a disc rotor connected to a wheel of the vehicle. In order to stop or slow the vehicle, pressure is applied by a brake caliper clamping brake pads against one or more outer surfaces of the disc rotor (e.g., using so-called disc brakes), thereby slowing or stopping the rotation the wheel.
Some rotors have a veined construction. A typical veined rotor 100 is depicted in FIGS. 1 and 2, wherein FIG. 1 shows a front view and FIG. 2 shows a side view of the rotor 100. A portion of the rotor 100 (between the lines I and II) is cut away to show the inside veined structure of the rotor. The veined rotor essentially is made up of two disc plates separated and connected by a number of veins. The veins can be straight or curved and the number of veins varies from one rotor to another. For example, FIGS. 3 and 4 show an example of an unmachined veined rotor with curved veins. The rotor 100 has two outside surfaces 102, 104, these surfaces being provided by the outer surfaces of the two discs comprising the rotor. It is against these two surfaces 102, 104 that pressure is applied (e.g., by brake pads (not shown)) in order to slow or stop the rotation of the wheel drive connected to the rotor 100. Ideally, the rotor 100 is perfectly circular and these surfaces 102, 104 are parallel to each other.
A typical rotor 100 is manufactured by machining a pre-cast rotor. A cast, pre-machined rotor 106 is shown in FIGS. 5 and 6 which depict front and side views of the pre-cast, un-machined rotor 100, respectively. The rotor 100 shown in FIGS. 1 and 2 is produced by appropriately machining the cast rotor 106.
A number of problems or defects can exist with existing rotors, and some of these problems or defects can be traced back to the manner in which the rotors were machined. For example, as noted above, in order to prevent or avoid uneven wear and heat of the rotors surfaces, the two surfaces 102, 104 are ideally parallel. In prior machining systems, the parallelness of the two surfaces was not determined prior to machining. Further, after machining, it is desirable to minimize thickness variation (TV) and lateral run-out (LRO) of each rotor as well as to have a symmetric rotors. A summary of these problems can be found in "Using Capacitive Probes in Automotive Brake Component Testing," Steve Muldoon and Rick Sandberg, Test Engineering & Management, August/September 1997 (hereinafter "Muldoon"). Muldoon is hereby incorporated herein in its entirety by reference. Muldoon shows the use of non-contact capacitance probes in post-production brake testing.